The present invention relates to an immobiliser system for a vehicle. It also relates to an immobiliser set comprising an immobiliser system and a switch key equipped with a transponder. The invention finds a particularly advantageous, but not exclusive, application in the management of a fleet of vehicles, for example for a car rental company.
In order to simplify the way of renting a vehicle, rental companies are largely implementing reservation systems via Internet or telephone. Such a reservation system may provide a user with an access code so as to unlock the vehicle. The access code may be entered via a keyboard placed on the outside of the vehicle or behind the windscreen. The user is so enabled to get into the vehicle, where the switch key may be left for starting the vehicle. Instead of an access code, regular users may be provided with an RFID card upon registration. The RFID card can then be “activated” on demand through the reservation system, so that when it is identified by a card reader mounted on the vehicle, it unlocks the vehicle. This reservation process shows obvious disadvantages as regards the security of the vehicle. Indeed, the switch key is left in the vehicle and an unauthorised person or a thief can break the lock of the vehicle and start the vehicle without any difficulty, even if the vehicle is equipped with a conventional immobiliser system.
A conventional immobiliser system, also known as an anti-theft security system, comprises a transmitter-receiver unit and a control unit. The transmitter-receiver unit is integrated near the ignition lock of the vehicle and can transmit an electromagnetic signal to a transponder integrated in the switch key. Said electromagnetic signal powers the transponder, which returns an answer signal containing an identification code. This code is generally stored in an electronic tag, for example an RFID tag, of the transponder. It is received by the transmitter-receiver unit and processed by the control unit for checking its validity and, if appropriate, for authorising the starting of the vehicle. The identification code can be encrypted in a variety of ways.
Some security systems have been developed for car rental applications. However, these security systems are not entirely satisfactory. As an example, document US 2001028295 describes an electronic key equipped with an intelligent system for receiving user “credits” from a control centre. The electronic key communicates bi-directionally with the vehicle. The latter has an electronic system in order to verify, from data contained in the electronic key, whether the user and his “credits” are valid and, if appropriate, to authorise the starting of the vehicle. However, such a system involves an electronic key containing additional functionalities. Such a customised switch key is obtained by substituting the original switch key with a dedicated switch key. One difficulty is to fit the switch key with an identification code that is accepted by the immobiliser system. In practice, the dedicated switch key is associated with the immobiliser system through an association process. This process is time consuming and generally implies the intervention of the car manufacturer. An additional drawback of this solution is that the switch keys are subjected to many shocks and can be easily damaged. Last but not least, the cost of the customised switch key is much greater in comparison with the original switch key.
Document FR 2 848 951 discloses another security system developed for car rental applications. The security system comprises, in a usual manner, an immobilising transponder integrated into the vehicle, and an electronic label intended to communicate with the transponder. However, the electronic label is integrated into the vehicle far enough away from the transponder so as to prevent any direct electromagnetic coupling. A passive relay is so provided so as to enable setting up or interrupting the communication between the transponder and the electronic label. The passive relay includes a first antenna close to the transponder, a second antenna close to the electronic label, and an electrical connection equipped with a switch for connecting the two antennas. This security system is well adapted for authorising the starting of the vehicle from a remote server. However, it suffers from the need to dismantle the original key to get the electronic label. Hence, there is a risk that the original key would be damaged during its dismantling. This entails a loss of value of the vehicle for the resale.
It is also known, from document U.S. Pat. No. 6,781,507, a remote starting system for a vehicle comprising a passive anti-theft security system. This remote starting system is not dedicated to a car rental application, but aims at enabling a user to remotely operate a vehicle. The system comprises a first coil arranged close to the ignition lock, a first transponder arranged in the switch key, a second transponder, similar to the first one, arranged in the vehicle close to the first coil, and a second coil wound around the second transponder. The second transponder may be used for starting the vehicle in the absence of the switch key. However, in order to maintain the functionality of the anti-theft security system, the second coil is closed via a relay. This has the effect of blocking the electromagnetic coupling between the second transponder and the first coil. When the vehicle is to be remotely started, the relay is opened, which allows the first coil to transmit a signal to the second transponder. The second transponder responds by sending an authorisation code to the first coil, thus allowing the starting of the vehicle. The invention described in document U.S. Pat. No. 6,781,507 does not alter the integrity of the anti-theft security system. However, it could not be adapted for a car rental application, insofar as it does not allow to remotely prevent the starting of the vehicle for a user in possession of the switch key.